Many inverter circuits and converter circuits are being used for power converters ranging from small power apparatuses such as an air conditioner and a microwave oven to large power apparatuses used in railroad, an iron mill, etc. In such inverter circuits and converter circuits, as will be described later, an insulated gate bipolar transistor (IGBT) that is a kind of a power semiconductor, a diode, etc. are used.
For example, a below-mentioned Patent Literature 1 discloses a semiconductor device 1 in which an IGBT 101 and a PIN diode 102 are formed integrally. Moreover, below-mentioned Nonpatent Literatures 1 and 2 also disclose semiconductor devices each of which has the IGBT and the diode built in the same semiconductor substrate.
Incidentally, a below-mentioned Patent Literature 2 discloses an IGBT that has a collector electrode 500, a p-layer 100 that contacts the collector electrode 500 with a low resistance, an n-layer 112 that is lower in carrier concentration than the p-layer 100, and a drift n−-layer 110 that is lower in carrier concentration than the n-layer 112. Moreover, a below-mentioned Nonpatent Literature 3 also discloses an IGBT that has a p-layer and an n-layer over a collector electrode.
Moreover, a below-mentioned Nonpatent Literature 4 discloses a p-n junction and a tunnel phenomenon of Ge; a below-mentioned Nonpatent Literature 5 discloses a vertical IGBT; and a below-mentioned Nonpatent Literature 6 discloses a technology of softening recovery of a diode element.